The present invention relates to an acoustic fluid machine which enables temperature gradient between a base having an actuator of acoustic resonator and the top end having a valve device for sucking and discharging fluid to be as small as possible.
As disclosed in U.S. patent application Ser. No. 10/922,383 filed Aug. 19, 2004 corresponding to Japanese Patent Pub. No. 2004-116309, there is provided an actuator that has a piston is provided in the base of a tapered acoustic resonator for generating in-tube wave motion by acoustic resonance, and a valve device for sucking and discharging fluid according to pressure fluctuation therein.
In the acoustic fluid machine, shape and size of the acoustic resonator are determined to generate the optimum resonance frequency when temperature of fluid is within a certain range. The optimum frequency renders the optimum sucking and discharging of fluid. Thus, if the resonance frequency is out of the certain range, compression ratio becomes smaller to make it impossible to achieve desired discharge pressure.
The resonance frequency varies with change in temperature of a resonator. By calculating resonance frequency, frequency of an actuator for the piston is changed to comply with the resonance frequency, thereby exhibiting desired sucking/discharging performance.
So it is necessary to change the actuator for the piston using arithmetic machine, which makes its structure more complicate and expensive.
Temperature in the acoustic resonator of the acoustic fluid machine is higher in the closed top end or at the valve device, while it is lower in the piston and actuator which generally opens to make temperature gradient larger. If the temperature gradient in the acoustic resonator is as small as possible, it will not be out of the determined resonance frequency or its deviation is as small as possible to render it within normal compression range.